Eyepiece for Pentax PF80ED

Hi, I have a Pentax PF80Ed scope, It can accept standard 1.25" eyepiece but not all the eyepiece can come into focus.

My UO18mm ortho, 32mm PL works, but UO5,7mm ortho and TV3x barlow won't. I am thinking to buy a 16mm Nagler T5 or 14mmUWA but not sure if they will work on this scope. Does anybody have any experience on it?

Thanks,
GY